Dosage of Mepivacaine in Ultrasound Axillary Block
Status:
Completed
Trial end date:
2010-09-01
Target enrollment:
Participant gender:
Summary
The use of ultrasonography as an adjunct to regional anesthesia has significantly increased
in recent years. Brachial plexus blockade by an axillary approach is amenable to the use of
ultrasound guidance. Real time sonography of nerve structures ensures an optimal distribution
of the block solution. When compared to other methods of nerve localization, sonography
decreases: failure rate procedure time and the onset time for blockade. Furthermore, the use
of ultrasound for peripheral nerve blockade demonstrates decreased procedure related
complications such as nerve injury and unintentional vascular puncture.
Traditional axillary block techniques relying on surface anatomical landmarks require large
volumes of local anesthetic, generally 40mL and greater. Utilizing the increased accuracy
offered by ultrasound, some studies have shown that low volumes of local anesthetic can yield
successful axillary plexus blockade. Therefore, the tradition of using large volumes of local
anesthetic for axillary blocks, even without ultrasound, may not be warranted.
Although recent investigations support using a low volume of local anesthetic for brachial
plexus blockade, there is a lack of outcome data from blinded randomised trials. The primary
objective of this study was to evaluate 2 different volumes of local anesthetic for axillary
blockade: 1) 20mL or 2) 30 mL. For the 2 different volumes used in this study, a 1.5%
solution of mepivacaine was chosen due to its widespread clinical use in axillary blocks,
which is secondary to: rapid onset of action, intermediate duration of effect, and relative
low cost. The primary outcome was block success rate for outpatients undergoing distal upper
limb surgery. Secondary objectives included comparing the 2 volumes with respect to: time
required to perform the block, and onset of sensory and motor blockade.